A endometriose (EDT) é caracterizada pela presença de tecido endometrial fora da cavidade uterina, e afeta mulheres em idade reprodutiva. Postulamos que alterações na frequência de células T reguladoras (Treg), natural killer (NK), supressoras mielóides (MDSC) e dendríticas (DC) no peritônio justificariam a redução da capacidade do sistema imune de reagir contra as células endometriais, permitindo sua implantação em locais ectópicos. Aqui, células Treg, NK, MDSC e DC foram quantificadas no fluido peritoneal (FP) e sangue de mulheres com EDT, a fim de associa-las ao desenvolvimento da doença; níveis de citocinas também foram avaliados. Na EDT, observou-se aumento na frequência de Treg, MDSC e DC no sangue e aparente redução destas no FP; ainda, a concentração de IL-12 foi menor no sangue comparadas ao grupo controle. Não foram observadas diferenças quanto às células NK e as outras citocinas analisadas. Os resultados indicam aumento da frequência de populações reguladoras em amostras de sangue de pacientes EDT, entretanto esses resultados não são refletidos no FP. / Endometriosis (EDT) is a gynecological disease characterized by the presence of endometrial cells out of the uterine cavity, which affects women in reproductive age. We postulated that alterations in the frequencies of regulatory T cells (Treg), natural killer cells (NK), myeloid-derived suppressor cells (MDSC) and dendritic cells (DC) in the peritoneum could justify the reduced capacity of the immune system to react to these ectopic endometrial cells, allowing them to invade distant tissues. Here, Treg, NK, MDSC and DC were quantified in the peritoneal fluid (PF) and peripheral blood (PB) of women with EDT, in order to associate them with the development of EDT; cytokine levels were also assessed. In EDT, higher frequencies of Treg, MDSC and DC in the PB and apparent lower frequencies of these cells in the PF were observed; IL-12 concentration was smaller in PB of EDT compared to control. No differences between groups were observed for NK cells and the other cytokines evaluated. The results indicate higher frequencies of regulatory cells in PB samples of EDT patients, although these findings were not reflected in PF samples.

INTRODUÇÃO: O fato do vírus da Hepatite C (HCV) estabelecer uma infecção crônica persistente, na maioria dos casos, mesmo sendo reconhecido e alvejado pelos sistemas imune inato e adaptativo sugere que o mesmo tenha desenvolvido estratégias eficazes para driblar a ação desses sistemas. O HCV interfere na fase inicial de ativação da resposta imune adaptativa alterando a função das células dendríticas (DCs), o que provavelmente leva a uma ativação deficiente das células natural killer (NKs) e de linfócitos T. Portanto, a realização de estudos sobre DCs e NKs na infecção pelo HCV se torna de fundamental importância para a compreensão da patogênese e persistência desta infecção. MÉTODOS: Foram selecionados indivíduos com resolução espontânea da infecção pelo HCV, indivíduos com infecção crônica e indivíduos saudáveis. A técnica de citometria de fluxo foi utilizada para a determinação da frequência e do fenótipo de células dendríticas e NKs nesses indivíduos. Além disso, foi avaliada a atividade citotóxica das células NKs sob estímulo de IL-12 e IL-18, e também da linhagem K-562. RESULTADOS: A frequência de DC mielóides (mDC) expressando CD86, nos indivíduos crônicos, foi elevada e uma correlação positiva com a carga viral foi observada. Na análise do ensaio funcional foi observado que as populações de células NKs CD7+ CD57+ apresentaram maior expressão da molécula CD107a e baixa produção de IFNy nos indivíduos com infecção crônica. A constante exposição das células imunes ao IFN-alfa, induzido durante a infecção pelo HCV, resulta na polarização do fenótipo citotóxico, caracterizado por células NK ativadas com elevado poder de degranulação, mas com deficiente produção de IFN-y. CONCLUSÕES: As frequências das células DCs e NKs eram semelhantes em todos os indivíduos. A expressão da molécula CD86 na superfície das mDCs pode ter sido induzida pela presença do HCV, uma vez que foi observada correlação positiva com a carga viral. Células NK citotóxicas, altamente diferenciadas e incapazes de produzir IFN-y foram as mais frequentes na infecção crônica pelo HCV. A baixa produção de IFN-y por parte dessas células é um dos fatores envolvidos na deficiente ativação de uma resposta imune adaptativa capaz de controlar a infecção pelo HCV / INTRODUCTION: Hepatitis C virus (HCV) develops a chronic persistent infection in most of the cases, even being recognized and targeted by the innate and adaptive immune systems, suggests that the virus have developed effective strategies to circumvent the action of these systems. HCV interferes in the initial activation of the adaptive immune response by altering the function of dendritic cells (DCs), which probably leads to a deficient activation of natural killer cells (NK) and T lymphocytes. Therefore, studies of DCs and NK in HCV infection are very important for understanding the pathogenesis and the persistence of this infection. METHODS: We selected subjects with spontaneous resolution of HCV infection, with chronic infection and healthy subjects. Flow Cytometry was used to determine the frequency and phenotype of dendritic cells and NK cells of these individuals. In addition, we evaluated the NK cell cytotoxic activity in response to stimulation of IL-12 and IL-18 and in co-cultivation with the cell line K-562. RESULTS: In individuals with chronic infection, the frequency of myeloid (m) DC cells expressing CD86 was elevated and a positive correlation between these cells and viral load was observed. It was observed in chronic infected individuals that NK cells co-expressing CD7 and CD57 showed higher expression of CD107a and low production of IFN gamma. The constant exposure of immune cells to IFN-alfa induced during HCV infection results in the polarization of cytotoxic phenotype characterized by activated NK cells with high power degranulation, but with impaired production of IFN-y. CONCLUSIONS: The frequency of DCs and NK cells were similar in all individuals. The expression of CD86 molecule on the surface of mDCs may have been induced by the presence of HCV, since a positive correlation was observed with viral load. Cytotoxic NK cells, highly differentiated and unable to produce IFN-y, were the most frequent in chronic HCV infection. The low production of IFN-y by these cells is one of the factors involved in the poor activation of an adaptive immune response able to control HCV infection

Les cellules lymphoïdes innées (ILCs) sont des populations cellulaires d’identification récente, mais leur rôle in vivo chez l’homme reste mal connu. Dans une 1ère étude, nous avons pu montrer qu’un déficit sévère en NK au cours de déficits immunitaires communs variables est associé à un risque accru de manifestations non infectieuses et infectieuses bactériennes sévères, suggérant un rôle protecteur non redondant des cellules NK lorsque le système immunitaire adaptatif n’est pas fonctionnel. Dans une 2ème étude, nous avons montré que des patients atteints de déficits immunitaires combinés sévères ɣc et JAK3 déficients n’ont pas d’ILCs. Après allogreffe de moelle osseuse, le nombre d’ILCs circulantes reste indétectable, sans manifestation clinique notable associée. Ces résultats sont en faveur d’une redondance des fonctions des ILCs chez l’homme, lorsque les fonctions T et B sont conservées. Nous avons ensuite étudié les modifications phénotypiques et fonctionnelles des cellules NK au cours du purpura thrombopénique immunologique, et observé un défaut de production d’interféron-ɣ par les cellules NK circulantes et une augmentation de la cytotoxicité dépendante des anticorps des cellules NK spléniques. Une inhibition des fonctions des cellules NK par les immunoglobulines polyvalentes est également mise en évidence. Enfin, une étude des ILCs circulantes au cours de la maladie associée aux IgG4 ainsi qu’une revue de la littérature sur l’étude des ILCs au cours des pathologies inflammatoires sont rapportées. En conclusion, l’apparente redondance des ILCs chez l’homme ainsi que leur implication en pathologies inflammatoires en font de potentielles cibles thérapeutiques. / Innate lymphoid cells (ILCs) are recently identified components of the immune system, but their functions in vivo in humans are still elusive. In a first study, we show in patients with common variable immunodeficiency that non-infectious inflammatory complications and severe bacterial infections were more frequent in patients with severe NK cell lymphopenia, indicating potential non-redundant immune functions of NK cells when the adaptive immune response is not optimal. In a second study, we observe that in patients with ɣc and JAK3 severe combined immunodeficiencies, all ILC subsets are absent. After hematopoietic stem cell transplantation, ILCs remain indetectable with no susceptibility to disease, suggesting that ILCs might be redundant and dispensable in humans, if T and B cells functions are preserved. In the second part of this thesis, we study phenotypic and functional modifications of NK cell compartment in primary immune thrombocytopenia. Interferon gamma production by the peripheral blood NK cells of ITP patients is decreased. In contrast, splenic NK cells of ITP patients tend to be more efficient in antibody-dependent cell cytotoxicity. Intravenous polyvalent immunoglobulins lead to the inhibition of blood NK cell activation. Finally, we present the preliminary results of a study investigating the modifications of circulating ILCs in IgG4-related disease, and present an extensive litterature review concerning the role of ILCs in inflammatory diseases. In conclusion, the apparent redundancy of ILCs for protective immunity and their pathogenic role in inflammatory diseases make their targeting in humans for therapeutic purposes particularly promising.

Le neuroblastome (NB) est la tumeur extra-crânienne la plus fréquente du jeune enfant. Malgré une thérapie multimodale très agressive, 40% des patients atteints de NB à haut risque rechutent. Le traitement de ces patients consiste à éliminer la tumeur par chirurgie, radiothérapie et chimiothérapie, à reconstituer la moelle osseuse par une greffe de cellules souches autologues et enfin à éliminer la maladie résiduelle (MRD) par une immunothérapie visant l’antigène GD2 exprimé par les neuroblastes. Notre étude préclinique a examiné l’efficacité de deux stratégies de traitements qui visent à potentialiser les thérapies actuelles et réduire leur toxicité. La première consiste à réduire la masse tumorale par la radiothérapie ciblée combinée à des radiosensibilisants. La deuxième approche est basée sur l’activation des cellules natural killer (NK) pour potentialiser l’effet de l’immunothérapie anti-GD2 et éliminer la MRD. L’autophagie est un processus catabolique qui élimine les protéines et organelles endommagées par différents stress incluant les irradiations. Par conséquent, inhiber l’autophagie pourrait sensibiliser les neuroblastes aux irradiations. Or, nous avons montré qu’étant très radiosensibles, les neuroblastes ne sont pas davantage éliminés par les irradiations quand ils sont traités avec un inhibiteur de l’autophagie. De plus, l’absence d’un inhibiteur efficace de l’autophagie à usage thérapeutique ne permet pas actuellement d’adopter cette approche. Notre étude a également permis de révéler une nouvelle approche de stimulation des cellules NK par les cellules dendritiques plasmacytoïdes (pDC) activées par un ligand du récepteur Toll-like, capable d’éradiquer la MRD et prévenir les rechutes de NB. Nos résultats ont permis, d’une part, d’élucider les mécanismes impliqués dans la lyse des cellules NK activées par les pDC contre les neuroblastes et, d’une autre part, de démontrer que l’axe pDC-NK chez le patient est fonctionnel, augmente l’efficacité de l’anti-GD2 et élimine efficacement les neuroblastes. Ainsi, l’immunothérapie par les cellules NK est une stratégie très prometteuse pour traiter le NB. Cette étude préclinique servira de base à l’élaboration d’un essai clinique pour traiter les enfants atteints de NB au CHU Sainte Justine. / Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. Despite aggressive multimodal therapy, 40% of patients with high-risk NB relapse. The current therapy comprises an induction treatment with chemotherapy and surgery, a consolidation treatment including radiotherapy and high-dose chemotherapy followed by bone marrow rescue with autologous hematopoietic stem cell transplantation and finally anti-GD2 immunotherapy targeting the disialoganglioside (GD2) antigen expressed by neuroblasts to treat minimal residual disease (MRD). Our preclinical study proposes two treatment strategies to potentiate current therapies and reduced toxicities. The first aim to reduce tumor mass by targeted radiotherapy combined with radiosensitizers. The second approach is based on the activation of natural killer (NK) cells to potentiate the effect of anti-GD2 therapy and eliminate MRD. Autophagy is a catabolic process that recycle damaged proteins and organelles, induced under various conditions of cellular stress including irradiation. Therefore, inhibiting autophagy could sensitize neuroblasts to irradiation. However, our study showed that neuroblasts were highly sensitive to irradiation and autophagy inhibitor failed to increase neuroblasts sensitization to irradiation. In addition, the absence of a potent autophagy inhibitor for therapeutic use does not allow this approach to be adopted. Our preclinical study demonstrated a novel approach based on NK cell stimulation with Toll-like activated plasmacytoid dendritic cells (pDC) that enhances the efficacy of anti-GD2 immunotherapy and prevent NB relapse. We elucidated the mechanisms involved in pDC-activated NK cells killing of neuroblasts. We further demonstrated that neuroblasts were efficiently killed by patient’s NK cells after stimulation by activated pDC. This is further increased by the addition of anti-GD2 antibody. Altogether, our study demonstrates that NK cell-based immunotherapy has a real potential to enhance anti-GD2 immunotherapy effect and prevent NB relapse. This preclinical study will serve as a basis for the development of a clinical trial to treat children with NB at CHU Sainte Justine.

Variation in the sequence of T cell epitopes between dengue virus (DENV) serotypes is believed to alter memory T cell responses during second heterologous infections contributing to pathology following DENV infection. We identified a highly conserved, novel, HLA-B57-restricted epitope on the DENV NS1 protein, NS126-34. We predicted higher frequencies of NS126-34-specific CD8+ T cells in PBMC from individuals undergoing secondary, rather than primary, DENV infection due to the expansion of memory CD8+T cells. We generated a tetramer against this epitope (B57-NS126-34TET) and used it to assess the frequencies and phenotype of antigen-specific T cells in samples from a clinical cohort of children with acute DENV infection established in Bangkok, Thailand. High tetramer-positive T cell frequencies during acute infection were seen in only 1 of 9 subjects with secondary infection. B57-NS126-34-specific, other DENV epitope-specific CD8+ T cells, as well as total CD8+ T cells, expressed an activated phenotype (CD69+ and/or CD38+) during acute infection. In contrast, expression of CD71 was largely limited to DENV-specific CD8+ T cells. In vitro stimulation of CD8+ T cell lines, generated against three different DENV epitopes, indicated that CD71 expression was differentially sensitive to stimulation by homologous and heterologous variant peptides with substantial upregulation of CD71 detected to peptides which also elicited strong functional responses. CD71 may therefore represent a useful marker of antigenspecific T cell activation. During the course of our analysis we found substantial binding of B57-NS126-34 TET to CD8- cells. We demonstrated that the B57-NS126-34 TET bound KIR3DL1, an inhibitory receptor on natural killer (NK) cells. NK sensitive target cells presenting the NS126-34 peptide in the context of HLA-B57 were able to dampen functional responses of only KIR3DL1+ NK cells. Analysis of the activation of an NK enriched population in our Thai cohort revealed peak activation during the critical time phase in patients with severe dengue illness, dengue hemorrhagic fever, compared to people with mild illness. Our data identified CD71 as biologically useful marker to study DENV-specific CD8+ T cell responses and highlighted the role of viral peptides in modulating NK cell activation through KIR-MHC class I interactions during DENV infection.

La cellule NK fait partie du système immunitaire inné et participe à l’immunosurveillance anti-tumorale. La compréhension des facteurs affectant leur biologie, telle que la génétique, est donc cruciale. Dans un premier temps, nous avons évalué le rôle de la sous-unité d’intégrine CD11d, sur le phénotype et l'expression d’autres sous-unités (CD11a, CD11b, CD11c, CD18) de diverses cellules immunitaires entre un modèle murin CD11d-KO et une souris C57BL/6 (B6). Nous avons remarqué que l'effet de la délétion de CD11d sur l'expression des autres sous-unités d'intégrine est spécifique à chaque type de cellule immunitaire. La différence la plus notable dans l'expression de CD11b et CD11c a été observée dans les cellules NK. La perte de CD11d dans les cellules NK a entraîné une diminution de l'expression de CD107a après leur activation, ce qui suggère une altération de la dégranulation des cellules NK. Ensuite, malgré une croissance de mélanome similaire, une plus grande proportion de cellules NK issues de CD11d-KO se sont accumulées dans les lits tumoraux par rapport à leur homologue B6. Dans un deuxième temps, nous avons exploité le modèle murin NOD, connu d’avoir des défauts immunitaires importants. L’acquisition des fonctions cytotoxiques des cellules NK se fait par un processus appelé maturation fonctionnelle où une cellule NK est d’abord CD27-CD11b-, suivi du stade CD27+CD11b-, puis CD27+CD11b+ et finalement CD27-CD11b+, soit le stade le plus mature et cytotoxique. Nous avons démontré que les cellules NK de la souris NOD produisent nettement moins d’IFN-γ, de TNFα et de Granzyme B et échouent à réguler l’expression du récepteur d’activation NKG2D pour chaque stade de maturation fonctionnelle. Finalement, nous avons traité des souris immunodéficientes porteuses de tumeurs avec des cellules NK de NOD et B6. Nous avons démontré que, tout comme pour les cellules NK de B6, ce sont surtout des cellules NK CD27+ de NOD qui s’accumulent dans les tumeurs. Par contre, les souris injectées avec des cellules de NOD montraient une croissance tumorale significativement plus importante. De manière générale, ces études sont les premières à élucider les impacts de l’absence de CD11d sur le phénotype et la fonction des cellules NK ainsi que leurs défauts fonctionnels dans la souris NOD au courant de leur maturation fonctionnelle. / NK cells are part of the innate immune system and participate in anti-tumor immunosurveillance. Understanding the factors affecting their biology, such as genetics, is therefore crucial. First, we evaluated the role of the integrin subunit CD11d on the phenotype and expression of other subunits (CD11a, CD11b, CD11c, CD18) of various immune cells between a CD11d-KO mouse model and a C57BL/6 (B6) mouse. We noted that the effect of CD11d deletion on the expression of other integrin subunits is specific to each immune cell type. The most notable difference in CD11b and CD11c expression was observed in NK cells. Loss of CD11d in NK cells resulted in decreased CD107a expression after their activation, suggesting impaired NK cell degranulation. Second, despite similar melanoma growth, a greater proportion of CD11d-KO-derived NK cells accumulated in tumor beds compared to their B6 counterpart. We then exploited the NOD mouse model, known to have significant immune defects. The acquisition of cytotoxic functions of NK cells occurs through a process called functional maturation where an NK cell is first CD27-CD11b-, followed by the CD27+CD11b- stage, then CD27+CD11b+ and finally CD27-CD11b+, the most mature and cytotoxic stage. We demonstrated that NK cells from NOD mice produce significantly less IFN-γ, TNFα, and Granzyme B and fail to regulate the expression of the activation receptor NKG2D for each stage of functional maturation. Finally, we treated immunodeficient tumor-bearing mice with NOD and B6 NK cells. We demonstrated that, as with B6 NK cells, NOD CD27+ NK cells predominantly accumulated in tumors. However, mice injected with NOD NK cells showed significantly greater tumor growth. Overall, these studies are the first to elucidate the impact of the absence of CD11d on the phenotype and function of NK cells as well as their functional defects in NOD mice during their functional maturation.

Le neuroblastome pédiatrique à haut risque est incurable malgré l’intensification des traitements. Chez le patient, les cellules de neuroblastome échappent à l’activité anticancéreuse des cellules immunitaires Natural Killer (NK). Or, lorsque cultivées in vitro en monocouche (2D), les cellules de neuroblastomes redeviennent sensibles à l’activité cytotoxique des cellules NK ce qui ne reflètent pas leur résistance dans les tumeurs in situ. Nous faisons l'hypothèse que lorsque cultivées en 3D sous forme de sphéroïdes, les cellules de neuroblastome pourraient retrouver certaines caractéristiques qui les rendraient plus représentatives des tumeurs in situ au niveau immunologique. Ainsi, un tel modèle préclinique pourrait mieux refléter la résistance aux cellules NK et servir de modèle de criblage pour la découverte de médicaments potentialisant la cytotoxicité des cellules NK. Pour répondre à cette question, nous avons développé un système de culture cellulaire 3D utilisant plusieurs lignées cellulaires de neuroblastome. À ce système, une co-culture en 3D avec une lignée de cellules Natural Killer (NK92) a été mise en place. Nous avons mis en évidence que les sphéroïdes de neuroblastome présentent des changements d’expression de certains gènes qui sont retrouvées chez les patients ainsi qu’une plus grande résistance à l’activité cytotoxique des cellules NK92 en comparaison avec les lignées en monocouche. Les co cultures de sphéroïdes ont été exposées à des inhibiteurs de protéines impliquées à différents niveaux de l’épigénome afin de découvrir des médicaments qui sensibiliseraient les cellules de neuroblastome à l’activité cytotoxique des NK92. Une différence dans la sensibilité aux médicaments entre les sphéroïdes et les cellules en 2D ainsi qu’en monoculture ou en co-culture a été observée et certains composés ont été identifiés en vue de potentialiser l’activité des cellules NK92. Ainsi, nos études ont permis de mieux comprendre les mécanismes impliqués dans la résistance des cellules du neuroblastome à l’activité cytotoxique des cellules NK dans un modèle plus représentatif de la tumeur in situ. / High-risk pediatric neuroblastoma remains incurable despite intensified treatments. In patients, neuroblastoma cells evade the anti-cancer activity of Natural Killer (NK) immune cells. However, when cultured in vitro in a monolayer (2D), neuroblastoma cells become sensitive to the cytotoxic activity of NK cells, which does not reflect their resistance in tumors in situ. We hypothesize that when cultured in 3D in the form of spheroids, neuroblastoma cells could regain certain characteristics that would make them representative of tumors in situ at the immunological level. Thus, such a preclinical model could better reflect NK cell resistance and serve as a screening model for drug discovery to discover a treatment that can potentiate NK cell cytotoxicity. To answer this question, we developed a 3D cell culture system using several neuroblastoma cell lines. To this system, a 3D coculture model with a Natural Killer (NK92) cell line was set up. We have shown that neuroblastoma spheroids develop changes in the expression of certain genes that are found in patients as well as greater resistance to NK92 cells compared to monolayer cell lines. Spheroid cocultures were exposed to inhibitors of proteins involved at different levels of the epigenome to discover drugs that would sensitize neuroblastoma cells to the cytotoxic activity of NK92. A difference in drug sensitivity between spheroids and cells in 2D as well as in monoculture or coculture was observed and some compounds were identified to potentiate the activity of NK92 cells. Thus, our studies have provided a better understanding of the mechanisms involved in the resistance of neuroblastoma cells to the cytotoxic activity of NK cells in a more representative model of the tumor in situ.

Die Selektion klonal expandierender Zellen mit einzigartigen, somatisch rekombinierten Anti-gen-Rezeptoren und die Langlebigkeit der daraus hervorgehenden Gedächtniszellen sind definierende Eigenschaften adaptiver Immunität. Dahingegen ist das angeborene Immunsystem da-rauf programmiert, mittels einer breiten Palette konservierter Rezeptoren möglichst schnell auf Pathogene zu reagieren und wird dabei auf Populationsebene epigenetisch geprägt. In dieser Arbeit möchte ich dieses Paradigma auf der Basis von Natürlichem Killer (NK) Zell-Gedächtnis an das humane Zytomegalievirus (HCMV) als Beispiel für Pathogen-spezifische Anpassung innerhalb des angeborenen Immunsystems herausfordern. Indem wir multiparametrische Einzel-zellanalysen zur Kartierung von ex vivo NK Zellen mit endogenen Barcodes in Form von soma-tischen Mutationen in mitochondrialer DNA (mtDNA) verknüpfen, können wir drastische klonale Expansionen adaptiver NK Zellen in HCMV+ Spendern nachweisen. NK-Zell-Klonotypen waren durch eine ihnen gemeinsame, inflammatorische Gedächtnissignatur mit AP1 Motiven gekennzeichnet, die eine Reihe einzigartiger Chromatin-Regionen mit Klon-spezifischer Zugänglichkeit überlagerte. NK-Zell-Klone wurden über einen Zeitraum von bis zu 19 Monaten stabil aufrechterhalten und behielten dabei ihre charakteristischen, Klon-spezifischen epigenetischen Signaturen, was die entscheidende Rolle klonaler Vererbung von Chromatin-Zugänglichkeit für die Prägung des epigenetischen Gedächtnis-Repertoires unterstreicht. Insgesamt identifiziert diese Arbeit zum ersten Mal klonale Expansion und Persistenz innerhalb des angeborenen Immunsystems im Menschen und deutet daraufhin, dass diese zentralen Mechanismen zur Ausbildung von immunologischem Gedächtnis evolutionär unabhängig von diversifizierten Antigen-Rezeptoren entstanden sind. / A hallmark of adaptive immunity is the clonal selection and expansion of cells with somatically diversified receptors and their long-term maintenance as memory cells. The innate immune system, in contrast, is wired to rapidly respond to pathogens via a broad set of germline-encoded receptors, acquiring epigenetic imprinting at the population level. The presented work challenges this paradigm by studying Natural Killer (NK) cell memory to human Cytomegalovirus (HCMV) infection as an example of pathogen-specific adaptation within the innate immune system. Leveraging single-cell multi-omic maps of ex vivo NK cells and somatic mitochondrial DNA (mtDNA) mutations as endogenous barcodes, we reveal drastic clonal expansions of adaptive NK cells in HCMV+ individuals. NK cell clonotypes were characterized by a convergent inflammatory memory signature driven by AP1 transcription factor activity, superimposed on a private set of clone-specific accessible chromatin regions. Strikingly, NK cell clones were stably maintained in their specific epigenetic states for up to 19 months, revealing that clonal inheritance of chromatin accessibility shapes the epigenetic memory repertoire. Together, this work presents the first identification of clonal expansion and persistence within the human innate immune system, suggesting these central mechanisms of immune memory have evolved independently of antigen-receptor diversification.

Dendritic cells (DCs) are professional antigen-presenting cells, which display an extraordinary capacity to induce T-cell responses. Recent findings revealed that DCs also play a crucial role in the activation of natural killer (NK) cells representing important effectors in the innate immune defense against viruses and tumors. Here, we summarize various studies investigating the bidirectional crosstalk between human DCs and NK cells. In this context, it has been reported that DCs efficiently enhance CD69 expression, proliferation, interferon (IFN)-γ secretion and cytotoxic activity of NK cells. Cell membrane-associated molecules as well as soluble factors such as interleukin-12, tumor necrosis factor-α and type I IFNs contributed to DC-mediated NK cell activation. Reciprocally, the ability of human NK cells to enhance the immunostimulatory capacity of DCs was shown. Thus, NK cells promoted the maturation of DCs and markedly augmented their capacity to produce proinflammatory cytokines and to stimulate T-cell responses. The NK cell-mediated effects on DCs were dependent on cell membrane-associated molecules such as NKp30 and soluble factors such as tumor necrosis factor-α and IFN-γ. In conclusion, the reciprocal activating interaction between human DCs and NK cells may play a pivotal role in the immune defense against viruses and tumors. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

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